what are the details behind Alice retests that changes spin results in QE exp.

[TakenItSeriously]

Assume Alice and Bob have a set agenda to test for the following case:

 

For a single given electron/positron entangled pair:

 

Alice measures X axes which should be 50:50 up or down

Bob measures Y axes which should be 3/4 the same or 1/4 different from Alice

Alice measures X axes ...?

 

I've heard form a recorded Richard Feinman lecture, that Alices X spin state can change after Bob measures a different spin state but he never gave any details behind that change.

 

What are the new odds for Alice's X measurement to change?

Must it always change?

Is it still 50:50 either way?

Does it depend on her last result?

Does it depend on Bob's last result?

Does it become a 1/4 same as Bobs Y result and 3/4 different from Bob's result?

 

I can't seem to find this answer anywhere though it's an awkward search.

Edited February 18, 2017 by TakenItSeriously

[swansont]

Assume Alice and Bob have a set agenda to test for the following case:

 

For a single given electron/positron entangled pair:

 

Alice measures X axes which should be 50:50 up or down

Bob measures Y axes which should be 3/4 the same or 1/4 different from Alice

Alice measures X axes ...?

 

I've heard form a recorded Richard Feinman lecture, that Alices X spin state can change after Bob measures a different spin state but he never gave any details behind that change.

 

 

Spin measurements along different axes does not commute (i.e. the result is not preserved) If you measure along X and then Y and the X again, you may not get the same result for X.

 

For entanglement to mean anything the measurement axes must be the same.

[TakenItSeriously]

Spin measurements along different axes does not commute (i.e. the result is not preserved) If you measure along X and then Y and the X again, you may not get the same result for X.

 

For entanglement to mean anything the measurement axes must be the same.

 

Ok, thanks.

 

The reason I had asked is that a girl had posted a hypothesis on youtube that I think I've heard before and I believe it's correct, though it could be very difficult to prove.

 

She did a good job describing it here:

https://youtu.be/z_6B2M12H9w

The mechanics:

The intrinsic angular momentum keeps the spin state of the electron locked at some angle due to a gyroscopic effect. Also their is a larmor procession that rotates the angle about a verticle axes that describe a cone.

 

Thats why all measurements are up or down regardless of the angle. All measurements are just measuring the verticle component of some arbitrary angle.

 

Note making the same measurement always produces the same result because the procession is about the verticle axes.

 

On the other hand alternating measurements keeps adding some amount of procession making results less certain.

 

Possible solution:

I believe tat the trick may be in control the precise amount of procession that gets added.

 

Then it should be possible to make some kind of predictionon about the cone size which finally allows for a prediction on the results.

 

It seems viable but would seem to depend mostly on precission of controlling the amount of procession.